And soon will come ''One From the Heart,'' a frantically stylized romance from Francis Coppola, of ''Godfather'' and ''Apocalypse Now'' fame. So far, it's been seen only in a ''preview'' edition--not a reviewable ''release'' version--and Coppola will probably make alterations before tossing it onto the market. But judging from the print shown the other night at Radio City Music Hall, it faces an uphill battle. Exquisite images and hummable pop songs can go just so far, weighed down with a listless love story and a drearily downbeat tempo.

Sandwiched between these offbeat items is ''Zoot Suit,'' another Hollywood oddity. Written and directed by Luis Valdez, based on his own play, it was filmed entirely on the stage of a Los Angeles theater. The story, set in the 1940s, focuses on a young Chicano who is charged with murder after a clash between rival gangs. Helped by an Anglo attorney and a crusader from the CIO, he and his codefendants battle for justice in a clearly biased courtroom. We follow the trial and learn about the facts through flashbacks to earlier events. Not likely material for a musical.

The filmmaker and his film deserve a lot of credit for courage. This is no ''West Side Story,'' full of back-alley realism and boisterous production numbers. It isn't even another ''One From the Heart,'' since Coppola uses his stagebound settings for lush visual effects, while Valdez goes for intimacy and streamlining. The musical numbers are brief and occasional, used to establish mood and period atmosphere, not to bolster a weak plotline.

In the end, though, ''Zoot Suit'' doesn't succeed. The literal staginess of the action seems claustrophobic after a while, and maneuvers that might work fine in the legitimate theater seem cramped and artificial in Panavision. The performances are uneven, and one key actor-- Edward James Almos as a mythical Chicano archetype-- is maddeningly monotonous in his ubiquitous role. For all its inventiveness and social conscience, ''Zoot Suit'' can't claim to have conquered the territory it so audaciously explores.

The failure of all these unconventional musicals is a pity, since Hollywood badly needs fresh ideas and approaches. Coppola was right at a recent press conference in New York, when he patted himself on the back for not just grinding out a predictable entertainment-- something he rarely does, anyway - and instead trying a whole new approach based on unusual ideas and the latest movie technology. Indeed, some critics have done him one better and chided audiences for not cheering a ''Pennies From Heaven'' simply because it has such chutzpah, regardless of what that chutzpah looks like on the screen.

It's tempting to agree with these observers and praise these films for their bold intentions alone-- in the hope that experimentation will become fashionable , eventually paying real dividends of art and entertainment. But there's no point in coaxing audiences to patronize movies whose laudable reach exceeds the feebleness of their grasp. What the new musicals try to do is exhilarating. What they succeed in doing is half baked.

Here's hoping Hollywood keeps up the struggle for freshness and innovation until it actually reaches a new plateau. Though it hasn't yielded positive results yet, the current effort is the most encouraging cinematic trend in ages.